1. Field of the Invention
The present invention relates to a ceramic rotary heat exchanger used in high temperature gases in a field of a gas turbine rotor, a stirling engine, etc. and to a method of manufacturing the same.
2. Related Art Statement
The known ceramic rotary heat exchanger has a disk shape 20 to 200 cm in diameter and 2 to 20 cm in thickness, and has a honeycomb structure. A ceramic rotary heat exchanger having a diameter under 30 cm can be simultaneously formed by an extrusion method. However, it is not possible to form a ceramic rotary heat exchanger having a diameter more than 30 cm by a single extrusion Therefore, such a ceramic rotary heat exchanger is formed by extruding ceramic matrix segments having a honeycomb structure and bonding the matrix segments together by means of an adhesion member such as ceramic and glass etc., as shown in Japanese Patent Laid-Open Publication No. 55-46338 or Japanese Patent Laid-Open Publication No. 63-263394.
Moreover, the ceramic rotary heat exchanger mentioned above has a ring gear arranged on its outer portion and is rotated by means of a pinion geared with the ring gear. One known method of securing the ring gear to the outer portion of the ceramic rotary heat exchanger is to arrange solid pins in the outer portion of the ceramic rotary heat exchanger and to secure the ring gear by means of springs arranged between respective solid pins. The other known method is that the ring gear is secured to the outer portion of the ceramic rotary heat exchanger having no pins by binding forces of an elastic member arranged thereon.
In the ceramic rotary heat exchanger mentioned above, outer peripheral portions at both ends of the rotary heat exchanger are sealed, and a high temperature gas is passed through an inner portion thereof, an outer portion thereof being exposed to the air. Therefore, an abrupt temperature gradient occurs in the ceramic rotary heat exchanger and thus thermal stresses are generated in the seal portion (including the pin portion).
In order to improve thermal shock properties a method, such as that disclosed in Japanese Patent Laid-Open Publication No. 1-147291, is known which employs a foaming joint member for connecting the ceramic matrix segments. Further, the ceramic rotary heat exchanger using the pins for securing the ring gear is affected by a mechanical stress due to a driving force concentrated on the pin portion as compared with the heat exchanger using no pins.
In a case in which use is made of a matrix segment connecting technique such that through hole directions of each of the segments are positioned in one direction, as shown in Japanese Patent Laid-Open Publication No. 55-46338 or Japanese Patent Laid-Open Publication No. 62-263394, a position of the solid pins 3, each arranged at a constant distance, is likely to be located at a connecting portion between the segments, as shown in FIG. 3. In this case, since a pin 3 is arranged at the connection portion between the segments and a connecting distance near the pin portion utilizing the foaming joint member becomes long, a foaming force generated during a sintering process becomes larger at the connection portion mentioned above. Further, in this case, since the segment has a soft structure, the foaming force is adsorbed at the connection portion between the segments only. However, since the solid pin has a hard structure the foaming force is not absorbed at the connecting portion, including the pins between the segments. Therefore, in this case, a thickness of the connecting portion becomes thicker and a crack is generated. As a result, there occur drawbacks such that a mechanical strength of the connecting portion 2 is decreased and a heat exchanging efficiency becomes lower due to a decrease of heat conduction area, etc.